If I ever had the chance to teach an art class, I would share one very important thing...don't be afraid to make mistakes. Mistakes are your friend. Mistakes can take the piece in a better direction. At the very least, even bad mistakes can be covered up or hidden.
For this 5 x 5, I used a picture of a setee from an Anthropologie catalog and a scrap of old ledger paper as the "floor". For the background, I used one of these fabric tags. It was a little too bold so I covered it in tissue paper. Still a little too bold. So I painted over it with a wash of vanilla paint. Then the tissue paper came off. Unintended? Yes. Totally cool look of aged plaster? Even better.
I finished the setee with a new paper seat and a new paper pillow. The only other thing I'd teach at a class is to lightly sand your finished work...tones the whole thing down a bit.